In 2014, when Russian President Vladimir Putin responded to a U.S.-backed coup that ousted a pro-Russian regime in Kyiv by occupying Crimea, President Barack Obama did nothing. When Putin aided secessionists in the Donbass in seizing Luhansk and Donetsk, once again, Obama did nothing. Why did we not come to the military assistance of Ukraine? Because Ukraine is not a member of NATO. We had no obligation to come to its aid. And to have intervened militarily on the side of Ukraine would have risked a war with Russia we had no desire to fight. Last year, when Putin marshaled...